My father's surmane was written Tirkel (rather Türkel with u umlaut) and this was my surname until 1969, when I was just 22 years old. Then I officially changed it to a popular Hebrew surname Tal.  My descision to change this surname was made in 1968, whan I was an air force cadet (serving in the IDF).  Here is the full story:

One morning our commander - Aviem Slavisizki aka Sela (who has been involved later in the Pollard fiasco) - ordered us to change our surnames to Hebrew names (he was promising us to participate in a delegation to the United States).  When he realized that I was not in a position to change my surname, he teased me, "would you like me to change it for you?".  My colleagues sarcastically called me, "Tirkul! Tirkul! change your name".  Then I made my decision, taking out all the letters in between TirkeL (Tal is written Hebrew TL).  During the following year I've gotten accustomed to my new name Tal and then applied the change it officially.

Olga, my mom, was quite upset when she heard about my decision to change our surname.  She had been a widow since 1948 - my late father, Israel-Menachem Turkel fell in the 1948 independance war. Then I consulted with our Turkel relatives.  The conflict was resolved following two phone calls. The first call was with my late cousin Adina nee Turkl and then with my late uncle, Eliezer Lippa Tirkel.  Adina reluctantly said that her husband Yosef had also changed his surname from Levkowski to Barlev, so she might not blame me...  Eliezer (Lippa) z"l - my uncle in Jerusalem - couldn't care less either.  Eliezer told me right away that he had considered to change his surname, from Tirkel to Tur Kal (Hebrew meaning light touring).  However, many people had known him by his original name.  Only therefore he had left it "as is".  Thereafter my decision to change my surname to Tal was final.